We are in the final stages of installing a new organ. It was about a 5 year project, start to finish. Ours is supposed to be very similar to this one in Houston:
http://www.stmartinsepiscopal.org/schoenstein.htm
These folks seem to deal in used organs:
http://www.organclearinghouse.com/services.php
It was a nice organ, but the "worship space" was built in the 60s, just like the Ugliest Cathedral in the World . . . so the acoustics naturally are hideous. Even a gaggle of acoustic engineers couldn't do much with it.